The present invention relates to a machine having automatic article transport, in particular a packaging machine, wherein individual like articles are moved along a conveyor path on a conveyor subdivided into unit lengths, which are each associated with one article, at a defined distance from each other past various processing stations.
In one known arrangement the machine comprises a clock which transmits a clock signal to a characteristic shift register associated with the conveyor path on advance of the conveyor by one unit length, and thereby shifts the information contained in the characteristic shift register on by one storage unit. A characteristic detection apparatus which is provided in the vicinity of the start of the conveyor path and which is connected to the input of the characteristic shift register, detects characteristics of the articles moving past which differ from the norm and transmits a corresponding electrical characteristic signal which is subsequently written into the characteristic shift register. An article sorting apparatus which is arranged at a later position of the conveyor path and which is connected to the characteristic shift register receives, at the instant an article moves past, the associated characteristic signal from the associated storage unit of the characteristic shift register and correspondingly sorts the relevant article.
In such machines with automatic article transport, and in particular automatic workpiece transport, such as is found in packaging machines, the information which accompanies the individual article (for example information formed at a control station as to whether the article is good or poor) is passed on in an electrical characteristic shift register in parallel to the physical transport of the article in the same rhythm as the article itself. A characteristic shift register of this kind is able to retransmit the stored information at any desired position, i.e. after any desired number of cycles or shifting steps, for example in order to bring about further processing steps such as sorting at subsequent processing stations. The term sorting is to be understood here in the broadest sense, i.e. that the article sorting apparatus may for example eject the article as unusable, or mark it as faulty in a suitable manner.
The decisive factor as to whether the associated information from the characteristic shift register is associated with the transported article at the appropriate station is the length of the shift register which is used which can in general be freely programmed. If this length in working cycles does not correspond to the corresponding distance moved by the article along the conveyor path, then the information stored in the shift register will be associated with the incorrect article.
Such faults in the association of article and characteristic signal in the vicinity of the article sorting apparatus can also arise when an article is present at the boundary between two unit length as a result of non-precise synchronisation of the conveyor with the clock, resulting in the next signal of the characteristic shift register being issued rather than the signal corresponding to the article. It is also possible that articles are removed in unauthorised manner from the conveyor path, or that they fall from the conveyor path between the characteristic detection apparatus and the article sorting apparatus. The danger of loss of synchronisation between the article transport and the transport of the characteristic information is particularly large when the conveyor path includes more or less large loops between the characteristic detection apparatus and the article sorting apparatus.
The object underlying the present invention is thus to provide a machine of the initially named kind with automatic article transport in which any faulty displacements between the transport of the articles on the conveyor path and the transport of the characteristic information in the characteristic shift register can be automatically detected.